JP5129820B2 - Space-time decoder and method for decoding Alamouti encoded signals in a high Doppler environment - Google Patents

Description

  Some embodiments of the invention relate to a wireless communication system. Some embodiments of the invention relate to a method for decoding an Alamouti encoded signal transmitted by multiple antennas in a high Doppler environment.

  Some conventional transmitters transmit special encoded signals using two or more antennas to increase the ability of the receiver to process those signals. For example, in some multiple-input multiple-output (MIMO) systems, an Alamouti encoded signal generated by a space-time encoder is transmitted to increase the decoding gain of a receiver, and the bit error rate (BER). Can be reduced. In a mobile environment, since the transmitter and / or receiver may move, the received symbols are distorted by Doppler shift. This distortion can reduce the decoding gain of the receiver and can significantly increase the receiver BER, especially at high SNR (signal-to-noise ratio) levels.

  Accordingly, there is a need for a receiver and method for decoding received signals that can be distorted by Doppler shift. There is also a need for a space-time decoder and method that increases decoding gain in a high Doppler shift environment.

1 illustrates a wireless communication system in some embodiments of the present invention.

FIG. 4 is a block diagram of a space-time decoder in some embodiments of the present invention.

6 is a flowchart illustrating a procedure for decoding a signal in a high Doppler shift channel in some embodiments of the invention.

  In the following description and drawings, a sufficient description is given to enable a person skilled in the art to practice certain embodiments of the invention. Other embodiments can be incorporated and structural, mechanical processes, and other changes are possible. The examples are only generally possible variations. Parts and features of some embodiments may be shown in or replaced with parts and features of other embodiments. Embodiments of the invention set forth in the claims include all available equivalents of those claims. Embodiments of the present invention are referred to herein individually or collectively as “the present invention” for convenience, but the present application is singled out when multiple embodiments are actually disclosed. It is not intended to be limited to any invention or inventive concept.

  FIG. 1 illustrates a wireless communication system in some embodiments of the present invention. The wireless communication system 100 may include a transmitter 102 and a receiver 106. The transmitter 102 may transmit a radio frequency (RF) signal received by the receiver 106 via the channel 104 using two or more antennas 112. Receiver 106 may receive an RF signal from transmitter 102 via channel 104 using one or more antennas 116.

当該マトリックスは、シンボル（α_０, α₁)のＡｌａｍｏｕｔｉ符号化送信に対応する。シンボルα_０, α₁は、送信機１０２で変調された入力ビットの振幅または位相を示す。当該送信マトリックスが示すように、第１の時点では、第１の送信アンテナがシンボルα_０を送信する間に第２の送信アンテナがシンボルα₁を送信してよい。第２の時点では、第１の送信アンテナがシンボル−α₁ ^＊を送信する間に第２の送信アンテナがシンボルα_０ ^＊を送信してよく、^＊は、複素共役を示す。これらの符号化されたシンボルは、送信機１０２内の時空間ブロックエンコーダによって生成されてよい。これは、２つ以上のアンテナ１１２を用いてデータストリームの多重コピーを生成し、データのさまざまな受信バージョンを利用してデータ転送の信頼性を高めるという技法である。その結果、受信機１０６のデコーディングゲインが向上し、および／または、ビット誤り率（ＢＥＲ）が減少しうる。 In some MIMO embodiments, transmitter 102 may transmit a pair of symbols (α ₀ , α ₁ ) encoded using antenna 112. In some embodiments, the transmitter 102 may encode the symbol (α ₀ , α ₁ ) according to the following transmission matrix:

The matrix corresponds to Alamouti encoded transmission of symbols (α ₀ , α ₁ ). Symbols α ₀ and α ₁ indicate the amplitude or phase of the input bits modulated by the transmitter 102. As indicated by the transmission matrix, at the first time, the second transmitting antenna may transmit the symbol α ₁ while the _first transmitting antenna transmits the symbol α ₀ . At the second time point, the second transmit antenna may transmit the symbol α ₀ ^* while the first transmit antenna transmits the symbol -α ₁ ^* , where ^* indicates a complex conjugate. These encoded symbols may be generated by a space-time block encoder in transmitter 102. This is a technique that uses two or more antennas 112 to generate multiple copies of a data stream and uses various received versions of the data to increase the reliability of the data transfer. As a result, the decoding gain of the receiver 106 can be improved and / or the bit error rate (BER) can be reduced.

In an embodiment using two transmit antennas 112 and one receive antenna 116, channel 104 may have two channels (shown as channels 113A and 113B) between transmitter 102 and receiver 106. Each of the channels may have different channel characteristics that may be represented by channel coefficients (h ₀ , h ₁ ) that indicate the channel transfer function of channel 104. As indicated by channel 104, a first channel 113A having a channel coefficient h ₀ acts on symbols -S ₁ ^* and S ₀ transmitted by the first transmit antenna 112 and has a second channel coefficient h ₁ . Channel 113B may act on symbols S ₀ ^* and S ₁ transmitted by second transmit antenna 112. The transmitted symbols S ₀ and S ₁ may correspond to the symbols α ₀ and α ₁ of the transmission matrix described above, respectively. As further shown, the signal from the channel 113A and 113B are coupled in the channel 104, the influence of noise indicated as n ₀ and n _1, it is received by receiver 106 as shown in FIG. Received symbols r ₀ and r ₁ are obtained. Received symbols r ₀ and r ₁ include complex numbers or values that are the result of integration of the signal received by receiver 106. The received symbols r ₀ and r ₁ are actually generated in the receiver 106 from the RF signal received via the antenna 116, but are shown in the channel 104 in FIG. 1 for purposes of illustration.

In situations where there is no Doppler shift (ie a stable channel), the received symbols r ₀ and r ₁ are represented by the following equations:

In these equations, R ₀ and R ₁ correspond to the received symbols r ₀ and r ₁ at the first and second time points, respectively, α ₀ and α ₁ represent the transmitted signals of the transmission matrix, h ₀ and h ₁ represents the channel coefficients of channels 113A and 113B, respectively, and n ₀ and n ₁ represent the average white Gaussian noise (AWGN) components at the first and second time points, respectively. In a conventional receiver, the decoder may evaluate the transmitted symbols α ₀ and α ₁ according to the following equation without taking noise into account.

これらの方程式において、δ_０は、チャネル１１３Ａのチャネル変化率を表し、δ_１は、チャネル１１３Ｂのチャネル変化率を表す。いくつかの実施形態では、受信機１０６内のチャネル推定器は、異なる時間に測定されたチャネル係数に基づき、チャネル変化率δ_０およびδ_１を計算してよい。これらの実施形態は、以下でさらに詳しく説明される。 In these equations, β ₀ and β ₁ represent output decisions from a conventional decoder. In a high Doppler environment where the transmitter or receiver is moving, the received symbols may be distorted due to the time dependence of the channel 104. A high Doppler shift may be caused by a situation in which the transmitter 102 and / or the receiver 106 move in a vehicle (eg, less than 300 km / h) such as an automobile or train. The strain can be represented by the following equation:

In these equations, δ ₀ represents the channel change rate of the channel 113A, and δ ₁ represents the channel change rate of the channel 113B. In some embodiments, the channel estimator in the receiver 106 may calculate the channel rate of change δ ₀ and δ ₁ based on the channel coefficients measured at different times. These embodiments are described in further detail below.

これらの値は、以下の方程式によっても表される。

これらの方程式は、前述された方程式（３）の安定したチャネルのケースでのＡｌａｍｏｕｔｉデコーダ出力と比べ、チャネル変化率δ_０およびδ_１によってβ_０およびβ_１が歪められたことを示す。 In a conventional receiver, the output of the Alamouti decoder can be shown as follows:

These values are also represented by the following equations:

These equations show that β ₀ and β ₁ are distorted by the channel change rates δ ₀ and δ ₁ compared to the Alamouti decoder output in the stable channel case of equation (3) described above.

According to some embodiments of the invention, the receiver 106 may include a space-time decoder that can compensate for time-dependent channel distortion due to high Doppler shifts. In some embodiments, the receiver 106 determines the soft symbol outputs v ₀ and v ₁ based on the received symbols r ₀ and r ₁ , channel change rates δ ₀ and δ ₁ , and channel coefficients h ₀ and h _{1. 1} is generated. These embodiments are described in detail below. In some embodiments, the space-time decoder generates hard symbol outputs x ₀ and x ₁ from soft symbol outputs v ₀ and v ₁ by performing maximum likelihood decoding. In some embodiments, the hard symbol outputs x ₀ and x ₁ are detected by detecting a point in the signal constellation having a minimum Euclidean distance to the soft symbol outputs v ₀ and v _1, thereby providing the soft symbol outputs v ₀ and v 1. ₁ may be calculated. These embodiments are described in further detail below.

In some embodiments, receiver 106 may receive initial hard symbol outputs x ₀ and x ₁ , received symbols r ₀ and r ₁ , channel change rate channel change rates δ ₀ and δ ₁ , and channel coefficient h _0. And h ₁ , modified soft symbol outputs θ ₀ and θ ₁ may also be generated. In these embodiments, the final hard symbol outputs x ₀ and x ₁ may be generated by performing maximum likelihood decoding on the modified soft symbol outputs θ ₀ and θ ₁ . These embodiments are described in further detail below. Channel rate of change δ ₀ and δ ₁ may be used to at least partially compensate for distortion in channel 104 due to high Doppler shift. In these embodiments, the final hard symbol outputs x ₀ and x ₁ generated by maximum likelihood decoding may be estimates of Alamouti encoded symbols α ₀ and α ₁ transmitted by transmitter 102. In some embodiments, the modified soft symbol outputs θ ₀ and θ ₁ and the provisional hard symbol output are generated iteratively to produce the final hard symbol outputs x ₀ and x ₁ , although the present invention The range is not limited to this.

Soft symbol outputs v ₀ and v ₁ (and modified soft symbol outputs θ ₀ and θ ₁ ) may indicate points in the complex plane corresponding to transmitted symbols α ₀ and α ₁ , respectively. The hard symbol outputs x ₀ and x ₁ may represent points in the signal point constellation having the minimum Euclidean distance to the corresponding soft symbol outputs v ₀ and v ₁ . If transmitter 102 uses binary phase shift keying (BPSK), hard symbol outputs x ₀ and x ₁ may have hard bit outputs and soft symbol outputs v ₀ and v ₁ may have soft bit outputs. So no further demodulation is necessary. In some non-BPSK embodiments, hard symbol outputs x ₀ and x ₁ are further demodulated in receiver 106 to produce hard bit outputs v ₀ and v ₁ , and soft symbol outputs v ₀ and v ₁ are May be further demodulated in the receiver 106 to produce a soft bit output. In these non-BPSK embodiments, the transmitter 102 modulates the symbol with a high modulation level, such as quadrature phase shift keying (QPSK) and eight phase shift keying, or quadrature amplitude modulation such as 16QAM or 64QAM. However, the scope of the present invention is not limited to this.

  FIG. 2 is a block diagram of a space-time decoder in some embodiments of the present invention. The space-time decoder 200 may be suitable for use in the receiver 106 (FIG. 1) and may compensate for time-dependent channel distortion due to high Doppler shift.

In some embodiments, the space-time decoder 200 includes received symbols (r ₀ , r ₁ ) 201, channel rate of change (δ ₀ , δ ₁ ) 205, and channel coefficients (h ₀ , h ₁ ) 203. And a combiner 206 that generates a soft symbol output (v ₀ , v ₁ ) 207. The space-time decoder 200 may also include a maximum likelihood detector 208 that performs maximum likelihood decoding and generates a hard symbol output (x ₀ , x ₁ ) 213 from the soft symbol output (v ₀ , v ₁ ) 207. .

In some embodiments, the hard symbol output (x ₀ , x ₁ ) 215 may be an initial hard symbol output. In some embodiments, the space-time decoder 200 includes an initial hard symbol output (x ₀ , x ₁ ) 215, received symbols (r ₀ , r ₁ ) 201, channel rate of change (δ ₀ , δ ₁ ) 205. And a collector 210 that generates a modified soft symbol output (θ ₀ , θ ₁ ) 211 based on the channel coefficients (h ₀ , h ₁ ) 203. In these embodiments, maximum likelihood detector 208 generates final hard symbol output (x ₀ , x ₁ ) 213 by performing maximum likelihood decoding on modified soft symbol output (θ ₀ , θ ₁ ) 211. You can do it.

In these embodiments, the received symbol (r ₀ , r ₁ ) 201 is an Alamouti encoded symbol (a pair of symbols s ₀ ,) transmitted by two or more transmit antennas, such as transmit antenna 112 (FIG. 1). s1 etc.). Combiner 206 and collector 210 may apply channel rate of change (δ ₀ , δ ₁ ) 205 to at least partially compensate for distortion in channel 104 (FIG. 1) due to high Doppler shift, but the scope of the present invention is It is not limited to this. In these embodiments, the final hard symbol output (x ₀ , x ₁ ) 213 generated by the maximum likelihood detector 208 is an estimate of the transmitted Alamouti encoded symbol (α ₀ , α ₁ ). It's okay.

In some embodiments, the space-time decoder 200 calculates channel coefficients (h ₀ , h ₁ ) 203 based on the training signals transmitted via channel 113A (FIG. 1) and channel 113B (FIG. 1). A channel coefficient estimator 202 may be included. In some embodiments, the channel coefficient estimator 202 may calculate the channel rate of change (δ ₀ , δ ₁ ) 205 from two or more sets of channel coefficients 203. In some embodiments, the channel coefficient estimator 202 is transmitted by the channel 113A (FIG. 1) and the channel 113B (FIG. 1) by transmitting the training signal separately (at different times) by each transmit antenna 112 (FIG. 1). The channel coefficient 203 of FIG. 1) can be determined individually.

In some embodiments, the collector 210 generates a modified soft symbol output (θ ₀ , θ ₁ ) 211 and the maximum likelihood detector 208 before generating a final hard symbol output (x ₀ , x ₁ ) 213. In addition, the provisional hard symbol output 215 is repeatedly generated (that is, one or more times), but the scope of the present invention is not limited thereto. In some embodiments, a single iteration may be sufficient.

  In some embodiments, the space-time decoder 200 may include a switching circuit 220 that switches the input of the maximum likelihood detector 208 from the output of the combiner 206 to the output of the collector 210. The space-time decoder 200 also switches the output of the maximum likelihood detector 208 to the input of the collector 210 when the collector 210 generates the modified soft symbol output 211 and the maximum likelihood detector 208 generates the provisional hard symbol output 215. A switching circuit 222 may also be included.

According to some embodiments, the received symbols (r ₀ , r ₁ ) 201 may include non-uniform received symbols. In these embodiments, the received symbols (r ₀ , r ₁ ) 201 may be processed by the combiner 206 without any prior channel coefficients being applied. Thus, in these embodiments, a channel equalizer is not necessary.

これらの方程式は、ドップラーシフトによる歪みを少なくとも一部補償しうる。これらの方程式において、ｒ_０は、第１の時点で受信されたシンボルを表し、ｒ_１は、第２の時点で受信されたシンボルを表し、ｈ_０は、チャネル１１３Ａ（図１）のチャネル係数を表し、ｈ_１は、チャネル１１３Ｂ（図１）のチャネル係数を表し、δ_０は、チャネル１１３Ａ（図１）の変化率を表し、δ_１は、チャネル１１３Ｂ（図１）の変化率を表し、^＊は、複素共役を表す。方程式（７）において、分母は、受信されたシンボルの振幅および位相をスケーリングするのに用いられる複素スケーリング係数である。 In some embodiments, combiner 206 may generate soft symbol output (v ₀ , v ₁ ) 207 substantially based on the following equation:

These equations can at least partially compensate for distortion due to Doppler shift. In these equations, r ₀ represents the symbol received at the first time point, r ₁ represents the symbol received at the second time point, and h ₀ is the channel coefficient of channel 113A (FIG. 1). H ₁ represents the channel coefficient of channel 113B (FIG. 1), δ ₀ represents the rate of change of channel 113A (FIG. 1), and δ ₁ represents the rate of change of channel 113B (FIG. 1). , ^* Represents a complex conjugate. In equation (7), the denominator is a complex scaling factor used to scale the amplitude and phase of the received symbol.

これらの方程式では、

は、軟シンボル出力ｖ_ｉに基づく最尤検出器２０８の暫定出力を表す。修正軟シンボル出力（θ_０，θ_１）２１１の値に基づき、最尤検出器２０８は、最終決定を硬シンボル出力２１３として生成してよい。 In some embodiments, additional processing may be performed. In these embodiments, the decision represented by the soft symbol output (v ₀ , v ₁ ) 207 may be further improved for high Doppler environments. In these embodiments, the collector 210 may generate a modified soft symbol output (θ ₀ , θ ₁ ) 211 substantially based on the following equation:

In these equations,

Represents the provisional output of the maximum likelihood detector 208 based on soft symbol output v _i. Based on the value of the modified soft symbol output (θ ₀ , θ ₁ ) 211, the maximum likelihood detector 208 may generate the final decision as the hard symbol output 213.

および、修正軟シンボル出力θ_ｉは、以下の方程式により表されるように再計算されてよい。

これらの実施形態では、修正軟シンボル出力θ_０およびθ_１として示される修正軟決定は、方程式（８）に従い計算されてよい。このプロセスは、何回か繰り返されてよいが、本発明の範囲はこれに限定されない。複素チャネルの変化率（δ_ｉ）に対してはレイリー分布を有し、分散が約０．２５の実数部および虚数部に対しては正規分布を有するチャネルにＢＰＳＫ変調を用いる実施形態では、標準的なＡｌａｍｏｕｔｉデコーディングにおけるＢＥＲを著しく減少させうるが、本発明の範囲はこれに限定されない。 In some embodiments, provisional output is used to increase decoder efficiency.

And the modified soft symbol output θ _i may be recalculated as represented by the following equation:

In these embodiments, the modified soft decisions shown as modified soft symbol outputs θ ₀ and θ ₁ may be calculated according to equation (8). This process may be repeated several times, but the scope of the present invention is not limited thereto. In an embodiment that uses BPSK modulation for a channel that has a Rayleigh distribution for the rate of change (δ _i ) of the complex channel and a normal distribution for the real and imaginary parts with a variance of about 0.25, the standard Although the BER in general Alamouti decoding can be significantly reduced, the scope of the present invention is not limited thereto.

  In some embodiments that communicate orthogonal frequency division multiplexing (OFDM) signals, the receiver 106 may derive a frequency domain signal corresponding to the received symbol 201 from a time domain signal received by the antenna 116 (FIG. 1). A Fourier transform circuit may also be included. In these embodiments, the receiver 106 may also include an error correction circuit such as a forward error correction (FEC) decoder that performs error correction decoding on the hard bit output and / or the soft bit output. The range is not limited to this. In some embodiments, the hard bit output and the soft bit output may be generated by demodulating the hard symbol output 213 and the soft symbol output 207, respectively. The receiver 106 (FIG. 1), although not individually illustrated, can be part of the physical layer of the receiver 106 and includes other functional components that generate a decoded bitstream corresponding to the transmitted symbols. You may have.

  Although the space-time decoder 200 is illustrated as having a number of individual functional components, one or more of the functional components may be combined or a processing element including a digital signal processor (DSP), etc. It may be implemented by a combination of software configuration elements and / or other hardware elements. For example, some elements may include one or more microprocessors, DSPs, application specific integrated circuits (ASICs), and various hardware and logic circuits that perform at least the functions described herein. Combinations may be included. In some embodiments, the functional elements of the space-time decoder 200 may refer to one or more processes that are performed on one or more processing elements.

  FIG. 3 is a flowchart illustrating a signal decoding procedure in a high Doppler shift channel according to some embodiments of the present invention. Procedure 300 may be performed by a space-time decoder, such as space-time decoder 200 (FIG. 1), but is applicable to other decoders. The procedure 300 is applicable to decoding signals in a channel with high Doppler shift, but can also be applied to decoding signals on channels with little Doppler shift.

In operation 302, channel coefficients (h ₀ , h ₁ ) are calculated. In some embodiments, channel coefficient estimator 202 (FIG. 1) may calculate one or more sets of channel coefficients based on a training signal received from a transmitter, such as transmitter 102 (FIG. 1). .

In operation 304, channel change rates (δ ₀ , δ ₁ ) are calculated based on the channel coefficients. In some embodiments, channel coefficient estimator 202 (FIG. 2) may calculate a channel change rate based on the channel coefficient generated in operation 302.

In operation 306, an initial soft symbol output (v ₀ , v ₁ ) is generated. In some embodiments, combiner 206 (FIG. 2) may be configured to receive received symbols (r ₀ , r ₁ ), channel rate of change (δ ₀ , δ ₁ ), and channel coefficients (h ₀ , h ₁ ). Based on this, initial soft symbol outputs v ₀ and v ₁ may be generated. In some embodiments, the initial soft symbol outputs v ₀ , v ₁ may be generated substantially based on equation (7) above.

In act 308, an initial hard symbol output (x ₀ , x ₁ ) is generated. In some embodiments, the initial hard symbol outputs x ₀ , x ₁ may be generated by the maximum likelihood detector 208 (FIG. 2) based on the initial soft symbol outputs v ₀ , v ₁ generated in operation 306. .

In operation 310, a modified soft symbol output (θ ₀ , θ ₁ ) is generated. In some embodiments, collector 210 (FIG. 2) includes initial hard symbol outputs x ₀ , x ₁ , received symbols r ₀ , r ₁ , channel rate of change δ ₀ , δ ₁ , and channel coefficient h _0. , H ₁ , modified soft symbol outputs θ ₀ , θ ₁ may be generated. In some embodiments, the modified soft symbol outputs θ ₀ , θ ₁ may be generated based on equation (8) above.

In operation 312, a modified hard symbol output (x ₀ , x ₁ ) is generated. In some embodiments, the modified hard symbol outputs x ₀ , x ₁ may be generated by the maximum likelihood detector 208 (FIG. 2) based on the modified soft symbol outputs θ ₀ , θ ₁ generated in operation 310. .

In operation 314, operations 310 and 312 may be repeated to generate a modified hard symbol output (x ₀ , x ₁ ). In some embodiments, operation 314 is optional. In these embodiments, the modified hard symbol outputs x ₀ , x ₁ may be generated by repeating operations 310 and 312 once, but the scope of the present invention is not limited thereto.

When operation 312 or 314 ends, the final hard symbol outputs x ₀ , x ₁ are processed to perform the next process of generating an output symbol stream that may correspond to the symbol stream encoded by transmitter 102 (FIG. 1). It may be provided by the space-time decoder 200 (FIG. 2). The output symbol stream may be demodulated based on the modulation level to generate an output bit stream that may correspond to the bit stream modulated by the transmitter 102 (FIG. 1).

  Although each operation of procedure 300 is illustrated and described as a separate operation, one or more of each operation may be performed simultaneously and the operations need not be performed in the order shown. .

  Returning to FIG. 1, in some embodiments, the transmitter 102 and the receiver 106 may communicate OFDM communication signals over a multi-carrier communication channel. The multicarrier communication channel may be in a predetermined frequency spectrum and may have a plurality of orthogonal subcarriers. In some embodiments, the multicarrier signal may be defined by a dense OFDM subcarrier. In some embodiments, transmitter 102 and receiver 106 may communicate according to a multiple access technique such as orthogonal frequency division multiple access (OFDMA), although the scope of the invention is not so limited. In some embodiments, transmitter 102 and receiver 106 may communicate using spread spectrum signals, although the scope of the invention is not so limited.

  In some embodiments, the transmitter 102 and / or the receiver 106 is one of a communication station, such as a WiFi communication station, an access point (AP), or a wireless LAN (WLAN) communication station including a mobile station (MS). Part. In some embodiments, transmitter 102 and / or receiver 106 may be part of a BWA (broadband wireless access) network communication station, such as a WiMax (Worldwide Interoperability for Microwave Access) communication station, although the present invention The range is not limited to this.

  In some embodiments, the transmitter 102 and / or receiver 106 may be a PDA (Personal Personal Digital Assistant), laptop, or portable computer, web tablet, wireless phone, wireless headset, with wireless communication capability, It may be part of a pager, instant messaging device, digital camera, access point, television, medical device (such as a heart rate meter, sphygmomanometer), or other device that can receive and / or transmit information wirelessly.

  In some embodiments, the frequency spectrum of communication signals used by transmitter 102 and receiver 106 may include a 5 GHz (GHz) frequency spectrum, or a 2.4 GHz frequency spectrum. In these embodiments, the 5 gigahertz (GHz) frequency spectrum may include frequencies in the range of about 4.9 to 5.9 GHz, and the 2.4 GHz frequency spectrum may be in the range of about 2.3 to 2.5 GHz. Frequency may be included, but the scope of the present invention is not limited to these, and other frequency spectra are applicable as well. In some embodiments of the BWA network, the frequency spectrum of the communication signal may include frequencies from 2 to 11 GHz, but the scope of the present invention is not limited thereto.

  In some embodiments, the transmitter 102 and the receiver 106 may be IEEE 802.11 (a), 802.11 (b), 802.11 (g), 802.11l (h) and / or 802.1l. (N) The communication may be performed in accordance with a specific communication standard such as an IEEE (American Institute of Electrical and Electronics Engineers) standard including a standard and / or a specification proposed for a wireless LAN, but the scope of the present invention is not limited thereto. It can also be applied to perform transmission and / or reception according to other techniques and standards. In some embodiments of the BWA network, the transmitter 102 and the receiver 106 may communicate according to various evolved WMAN (Wireless Metropolitan Network) IEEE 802.16-2004 and IEEE 802.16 (e) standards. However, the scope of the present invention is not limited to these, and can be applied to perform transmission and / or reception according to other technologies or standards. Further information regarding the IEEE 802.11 and IEEE 802.16 standards can be found in "IEEE Standards for Information Technology-Telecommunications and Information Exchange Between Systems-Local Area Networks-Specific Requirements-Part 11," Wireless LAN Medium Access Control (MAC) And Physical Layer (PHY), ISO / IEC 8802-11: 1999 ”, and Metropolitan Area Network—Specific Requirements—Part 16,“ Air Interface for Fixed Broadband Access Systems ”, May 2005, and related revisions. I want to be. Some embodiments relate to IEEE 802.11e intended to enhance the IEEE 802.11 WLAN specification with quality of service (QoS) functions including data prioritization, voice and video communications.

  Transmit antenna 112 and receive antenna 116 may include one or more directivities including, for example, a dipole antenna, monopole antenna, patch antenna, loop antenna, microstrip antenna, or other type of antenna suitable for transmitting RF signals. Or an omnidirectional antenna may be included. In some embodiments of MIMO (Multiple Input Multiple Output), more than one antenna may be used. In some embodiments, a single antenna with multiple apertures may be used instead of two or more antennas. In these embodiments, each aperture may be considered a separate antenna.

  In some other embodiments, the transmitter 102 and the receiver 106 may communicate according to a standard, such as a pan-European mobile system standard called GSM (Global System for Mobile Communications). The transmitter 102 and the receiver 106 may operate in accordance with a packet radio communication service such as a GPRS (General Packet Radio Service) packet data communication service. In some embodiments, the transmitter 102 and the receiver 106 are, for example, 2.5G and 3G radio standards (3GPP technical specifications, version 3.2.0, 2000, including 3GPP LTE (Long Term Evolution). Communication may be performed according to the UMTS (Universal Mobile Telephone System) for the next generation GSM, which may implement communication technology according to (see March). In some of these embodiments, transmitter 102 and receiver 106 may provide a packet data service (PDS) that utilizes a packet data protocol (PDP). In some embodiments, the transmitter 102 and the receiver 106 may be referred to other standards or the enhanced data for GSM evolution (EDGE) standard (3GPP technical specification, version 3.2.0, March 2000). May be communicated according to other air interfaces, including interfaces compatible with, but the scope of the present invention is not so limited.

  Unless otherwise stated, terms such as processing, calculation, calculation, determination, display, etc. process data expressed as physical (electronic) quantities in the registers and memory of the processing system, and physical quantities in the registers or memory of the processing system Of one or more processing or computing systems, or similar devices, or other such information storage, transmission, or display device operations and / or processes that may be converted to other data that is also represented as You may point to that. Further, a computing device as used herein has one or more computing units coupled to a computer readable memory that can be volatile or non-volatile memory, or a combination thereof.

  Some embodiments of the invention may be implemented in one or a combination of hardware, firmware, and software. Embodiments of the invention may be implemented as instructions stored on a machine-readable medium that may be read and executed by at least one processor that performs the operations described herein. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (eg, a computer). For example, a machine readable medium may be a ROM (Read Only Memory), a RAM (Random Access Memory), a magnetic disk storage medium, an optical storage medium, a flash memory device, an electrical, optical, acoustic wave, or other form of propagation signal (eg, Carrier waves, infrared signals, digital signals, etc.), and others.

  The abstract makes it possible for the reader to confirm the nature and gist of the technical disclosure in accordance with US Patent Enforcement Regulation 1.72 (b). It is submitted with the understanding that it will not be used to limit or interpret the scope and spirit of the invention. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment.

Claims (20)

A space-time decoder,
A combiner that generates a soft symbol output based on the received symbols, channel rate of change, and channel coefficients;
A maximum likelihood detector that performs maximum likelihood decoding and generates a hard symbol output based on the soft symbol output;
Equipped with a,
The hard symbol output is an initial hard symbol output;
The space-time decoder further comprises a collector that generates a modified soft symbol output based on the initial hard symbol output, the received symbol, the channel rate of change, and the channel coefficient;
The maximum likelihood detector generates a final hard symbol output by performing maximum likelihood decoding on the modified soft symbol output;
Space-time decoder. The received symbols include Alamouti encoded symbols transmitted by two transmit antennas,
The combiner and the collector at least partially compensate for distortion in the channel caused by high Doppler shift by applying the channel rate of change;
The final hard symbol output generated by the maximum likelihood detector is an estimate of the transmitted Alamouti encoded symbol;
The space-time decoder according to claim 1 . The received symbols include non-uniform received symbols;
The space-time decoder according to claim 2 . A channel coefficient estimator that calculates the channel coefficient based on a training signal transmitted over two or more channels between a transmitter and a receiver;
The channel coefficient estimator further calculates the channel change rate based on two or more sets of the channel coefficients;
The space-time decoder according to any one of claims 1 to 3 . Before generating the final hard symbol output, the generation of the modified soft symbol output by the collector and the generation of a provisional hard symbol output by the maximum likelihood detector are iteratively performed.
The space-time decoder according to any one of claims 1 to 4 . If the collector and the maximum likelihood detector repeatedly generate provisional hard symbol output,
Switching the input of the maximum likelihood detector from the output of the combiner to the output of the collector;
A switching circuit for switching the output of the maximum likelihood detector to the input of the collector;
The space-time decoder according to claim 5. The channel change rate includes a channel change rate of a first channel between a transmitter and a receiver and a channel change rate of a second channel between the transmitter and the receiver;
The channel coefficient includes a channel coefficient of the first channel and a channel coefficient of the second channel;
The received symbols include first and second consecutively received symbols;
The combiner multiplies the value obtained by adding the complex conjugate of the channel change rate of the first channel to 1 and the complex conjugate of the channel coefficient of the first channel and the first received signal. Generating a first soft symbol output based on the value;
The space-time decoder according to any one of claims 1 to 6 . The combiner multiplies the complex conjugate of the channel coefficient of the second channel by the value obtained by adding 1 to the complex conjugate of the channel change rate of the second channel and the first received signal. Generating a second soft symbol output based on
The space-time decoder according to claim 7 . The received symbol is a frequency domain signal according to an orthogonal frequency division multiplexing (OFDM) scheme, and is generated by performing a Fourier transform on the received time domain signal.
The space-time decoder according to any one of claims 1 to 8 . A method for decoding received symbols, comprising:
Generating a soft symbol output based on the received symbols, channel rate of change, and channel coefficients;
Performing maximum likelihood decoding and generating a hard symbol output based on the soft symbol output;
Equipped with a,
The hard symbol output is an initial hard symbol output;
The method
Generating a modified soft symbol output based on the initial hard symbol output, the received symbol, the channel rate of change, and the channel coefficient;
Generating a final hard symbol output by performing maximum likelihood decoding on the modified soft symbol output;
Further comprising
Method. The received symbols include Alamouti encoded symbols transmitted by two transmit antennas,
The method
Further comprising at least partially compensating for distortion in the channel caused by high Doppler shift by applying the channel change rate;
The final hard symbol output includes an estimate of the transmitted Alamouti encoded symbol;
The method of claim 10 . The received symbols are non-uniform received symbols;
The method of claim 11 . Calculating the channel coefficient based on a training signal transmitted over two or more channels between a transmitter and a receiver;
Calculating the channel rate of change based on two or more sets of the channel coefficients;
The method according to any one of claims 10 to 12 . Prior to the step of generating the final hard symbol output, further comprising the step of repeatedly generating the modified soft symbol output and the provisional hard symbol output.
14. A method according to any one of claims 10 to 13 . The soft symbol output is generated by a combiner, the provisional hard symbol output and the final hard symbol output are generated by a maximum likelihood detector, and the modified soft symbol output is generated by a collector;
The method
Switching the input of the maximum likelihood detector from the output of the combiner to the output of the collector;
When the collector and the maximum likelihood detector repeatedly generate the provisional hard symbol output, switching the output of the maximum likelihood detector to the input of the collector;
Further comprising
The method according to claim 14 . The received symbol is a frequency domain signal according to an orthogonal frequency division multiplexing (OFDM) scheme, and is generated by performing a Fourier transform on the received time domain signal.
The method according to any one of claims 10 to 15 . A space-time decoder with a combiner and a maximum likelihood detector;
A substantially omnidirectional antenna for receiving a signal including the received symbol;
With
The combiner generates a soft symbol output based on the received symbols, channel rate of change, and channel coefficients;
The maximum likelihood detector performs maximum likelihood decoding to generate a hard symbol output based on the soft symbol output;
The hard symbol output is an initial hard symbol output;
The space-time decoder further comprises a collector that generates a modified soft symbol output based on the initial hard symbol output, the received symbol, the channel rate of change, and the channel coefficient;
The maximum likelihood detector generates a final hard symbol output by performing maximum likelihood decoding on the modified soft symbol output;
Receiving machine. The received symbols include Alamouti encoded symbols transmitted by two transmit antennas,
The combiner and the collector at least partially compensate for distortion in the channel caused by high Doppler shift by applying the channel rate of change;
The final hard symbol output generated by the maximum likelihood detector is an estimate of the transmitted Alamouti encoded symbol;
The receiver according to claim 17 . A channel coefficient estimator that calculates the channel coefficient based on a training signal transmitted over two or more channels between the transmitter and the receiver;
The channel coefficient estimator further calculates the channel change rate based on two or more sets of the channel coefficients;
The receiver according to claim 17 or 18 . Before generating the final hard symbol output, the generation of the modified soft symbol output by the collector and the generation of a provisional hard symbol output by the maximum likelihood detector are iteratively performed.
The receiver according to any one of claims 17 to 19 .

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